Hitler came to power in 1933 when he was appointed as Chancellor of Germany (something like a Prime Minister in Great Britain). He was appointed by Paul von Hindenburg, the President of Germany at the time. Hindenburg appointed him because Hitler's Nazi Party had been becoming more popular and it was thought Hitler could help bring support for the government.

The Third Reich is what the Nazis called Germany during their rule. "Reich" means something like "empire" or "nation" or "kingdom." The Nazis felt that their regime was the third true German nation or empire in history.